1. Field of the Invention
The present invention relates to an imaging lens assembly, and more particularly, to a compact imaging lens assembly used in a mobile phone camera.
2. Description of the Prior Art
In recent years, with the popularity of mobile phone cameras, the demand for compact imaging lenses is increasing, and the sensor of a general photographing camera is none other than CCD (charge coupled device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, as advanced semiconductor manufacturing technology has allowed the pixel size of sensors to be reduced and the resolution of compact imaging lenses has gradually increased, there is an increasing demand for compact imaging lenses featuring better image quality.
A conventional imaging lens assembly for mobile phone cameras, such as the one disclosed in U.S. Pat. No. 7,365,920, generally comprises four lens elements and an aperture stop disposed in front of the four lens elements, wherein two spherical-surface glass lenses are used as the first and second lens elements, and being adhered together to form a doublet and thereby to correct the chromatic aberration. Such an arrangement of optical elements, however, has the following disadvantages: (1) the freedom of the system is curtailed due to the employment of excess number of spherical-surface glass lenses, thus the total track length of the system cannot be reduced easily; (2) the process of making the glass lenses adhered together is complicated, posing difficulties in manufacture.
U.S. Pat. No. 7,277,238 provides an imaging lens array comprising four respective lenses wherein a plurality of lenses are double-sided aspherical lenses so that the total track length of the system can be effectively reduced and the image quality can be improved as well. However, placing the aperture stop in front of the first lens element increases the sensitivity of the system, making it more difficult to control the manufacturing yields of the lens assembly.
Therefore, a need exists in the art for an imaging lens assembly that requires simple manufacturing process, maintains a proper total track length and a moderate sensitivity and is applicable to high-resolution mobile phone cameras.